A small segment of bone (and overlying cartilage) in the knee begins to separate from its surrounding region due to a lack of blood supply.

How Common: The condition heavily favours adolescents and also favours boys, so it is common in the young male athletic population. Overall incidence is 10 per 1 lac.

Average patient: A 15-year-old boy has constant knee pain while playing cricket.

Cause: Repetitive micro-trauma to the knee from high-impact activities and genetic associations have been postulated. Exact cause is yet unknown.

Symptoms: Pain and swelling of the knee often brought on by sports or physical activity. Advanced cases of OCD (loose body) may cause joint catching or locking.

What to do: Early diagnosis is important. This problem is non-urgent and can be evaluated at a clinic visit except if the piece is displaced and the knee is locked as a result of the loose piece getting between the bones in the knee (emergency!)

Severity of injury: This is based on biological age (whether one’s growth plates are still open) and whether the lesion is still attached or is partially/completely detached

Treatment options: For milder cases, resting, avoiding vigorous sports and bracing to unload the knee may be enough. For those cases in which the lesion is partially or completely detached, especially in adults, surgery is indicated. There are different surgical techniques for treating OCD;

• Drill (Microfracture) into the lesion to create pathways for new blood vessels.

• Hold the lesion in place with internal fixation (such as pins and screws).

• Replace the damaged area with a new piece of bone & cartilage (called graft).

• Attempt to grow new cartilage in the original defect (chondrocyte implantation)

Expected result: In children or adolescents with open growth plates, the affected bone and cartilage heal on their own. In adults, OCD lesions have a greater chance of separating. They can detach and float inside the joint, warranting surgery and possible issues in the years to come.

Return-to-activity timeline: Most children start to feel better over a 2-4 month course of rest and non-surgical treatment. They usually return to all activities as symptoms improve. Post-surgery, patients are usually non-weight bearing for 6-8 weeks and are then allowed to slowly wean off the walker/crutches. These lesions can take 5-7 months to heal. Patients are closely evaluated over several years - with interval x-rays and MRI - to make sure that the surgery was successful.